The present invention relates to a vacuum type solar heat collecting apparatus wherein a cylindrical water-reservoir is disposed in a glass container.
The conventional vacuum type solar heat collecting apparatuses which are generally used have a construction that a thin heat collecting pipe having a heat collecting plate is disposed in a transparent outer pipe whose interior is kept in vacuum, and a depression is installed at the center part of the heat collecting plate, and a heat collecting pipe which is a passage for a medium such as water is fitted into this depression.
The above-mentioned solar heat collecting apparatuses having the conventional construction have problems such that they are likely to produce loss of heat conduction from the heat collecting plate to the heat collecting pipe. The heat conduction loss is increased particularly when a relative movement or separation takes place. Incident energy is decreased due to a large loss in quantity of light when the solar light plunges obliquely into the heat collecting plate. The heat collecting pipe is thin and the amount of medium which can be heated at a time is limited. Therefore, another hot water storage tank has to be employed. The hot water feeding installation becomes expensive and much labor is taken for installation thereof.
This means that in the above-mentioned conventional hot water feeding installation, a circulating pump or the like is required for raising the temperature of hot water in the hot water storage tank by circulating water between the hot water storage tank and the heat collecting pipe. This requires an adiabatic construction dedicated to decreasing heat dissipation from the hot water storage tank and the circulating path.
Also, the conventional hot water feeding installations have a problem that when the heat collecting pipe is replenished with new water, the new water is mixed immediately with hot water in the heat collecting pipe, reducing the temperature of the hot water.
The present invention is performed in the light of the above-mentioned, and an apparatus of the present invention comprises a transparent long cylindrical glass container one end of which is sealed tightly and the other end of which is narrowed in a small diameter and opened. A cylindrical metal water-reservoir one end of which is sealed tightly and the other end of which is narrowed in a small diameter and opened, and disposed in the above-mentioned glass container in a coaxial fashion through supporters. The outer surface of the metal reservoir is coated with a selective absorption film. A first long pipe is inserted into the vicinity of the sealed end in the water-reservoir in a manner of penetrating the open ends of the above-mentioned glass container and water-reservoir. A second short pipe which is connected to the open end of the water-reservoir in a manner of penetrating the open end of the above-mentioned glass container. A sealing metal fixture seals the opening part of small diameter of the above-mentioned glass container. The space between the above-mentioned glass container and water-reservoir is kept in vacuum. Water is fed into the water reservoir through either of the above-mentioned first pipe and second pipe, and is stored and collects heat in the water-reservoir, being taken as hot water.
The present invention comprises the case where the open ends of the above-mentioned glass container and water-reservoir are disposed lower than the sealed ends thereof. Water is fed into the water-reservoir through the second pipe. Hot water is taken out of the water-reservoir through the first pipe or the second pipe. In the case where the above-mentioned open ends are disposed higher than the sealed ends thereof, water is fed into the water-reservoir through the first pipe, and hot water is taken out of the water-reservoir through the second pipe.
The present invention comprises also the case where the diameter of the second pipe is made larger than that of the first pipe to provide a gap around the outer periphery of the first tube and both pipes are disposed in a coaxial fashion, and the case where the first pipe and the second pipe are disposed in a parallel fashion.
Furthermore, the water-reservoir in accordance with the present invention comprises a configuration wherein outer peripheral parts of small diameter are provided at the both ends thereof and proper intermediate position, and the water-reservoir is disposed in the glass container in a coaxial fashion through supporters attached to these outer peripheral parts of small diameter.
Also the water-reservoir in accordance with the present invention comprises a configuration comprising a metal cylinder which has openings at opposite ends thereof and has a uniform diameter except for the intermediate portions where the supporters are attached and a metal cap jointed to the opposite ends of the cylinder.
Also, the present invention comprises a configuration wherein a plurality of glass containers having the water-reservoir therein are employed, and are connected to a first header pipe and a second heater pipe, respectively, in a parallel fashion through the first pipe and the second pipe.
Furthermore, the present invention comprises also a configuration wherein the header pipe of the water feed side is connected directly to a water feed pressure source, such as water service, through a reduced pressure check valve, and the header pipe at the hot water side is connected to a hot water feed pipe having a hot water feed stopcock.
In a vacuum type solar heat collecting apparatus in accordance with the present invention, the cylindrical metal water-reservoir disposed in the glass container has an outer diameter close to the inner diameter of the glass container, and is as sufficiently large to occupy a volume which is at least 60% or more of the inner volume of the glass container, and a large amount of water is stored therein. Then, the solar heat transmitted through the transparent glass container is collected in the metal water-reservoir through a selective absorption film. The heat collected in the metal water-reservoir is prevented from dissipation due to heat conduction toward the outside by a vacuum adiabatic action, and heats water in the water-reservoir. The temperature of the whole water in the above-mentioned water-reservoir is raised because the portion whose specific gravity becomes smaller due to warm-up by solar heat moves to the upper portion in the water-reservoir and natural circulation takes place in the water-reservoir.
In one embodiment in accordance with the present invention, the water pressure from the water feed pressure source, such as water service, is reduced to an appropriate pressure and acts through the reduced pressure check valve in each water-reservoir, the first and the second header pipes and the hot water feed pipe. When the hot water feed stopcock connected to the hot water feed pipe is opened, hot water in each water-reservoir is taken out and water of an amount equal to this discharge is fed from the water feed pressure source such as water service.
In the vacuum type solar heat collecting apparatus in accordance with the present invention, in the case where the open ends of the glass container and the water-reservoir are disposed lower than the sealed ends thereof and the apparatus is installed on the roof of a building or the like, water is fed into the water-reservoir through the second pipe from the second heater pipe connected directly to the water feed pressure source, such as water service, through the reduced pressure check valve. In this case, air in the water-reservoir goes outside, via the first pipe and the first header pipe and through an automatic air discharge valve attached to the end of the first header pipe, or the like, to be replaced by the water to be fed. The water level of the stored water in the water-reservoir is determined by the length of insertion of the first pipe. Therefore, the first pipe is inserted into the vicinity of the sealed end of the water-reservoir and the water level of the stored water is raised. The hot water in the water-reservoir is taken out via the first pipe and the first header pipe and through the hot water feed pipe connected thereto. In this case, when hot water in the water-reservoir is fed from the bottom part thereof, so as not to stir through the second header pipe disposed at the lower side of inclination and the second pipe, only hot water is taken out effectively because the hot water is pushed upward due to a difference of specific gravity between cold water and hot water. Water of an amount equal to that of the hot water taken out is fed from the second header pipe through the second pipe.
Hot water is taken out also by another method, wherein hot water is taken out from the second pipe via the second header pipe. In this case, one end of the second header pipe is connected to the water feed source, through an automatic or manual open/close valve, and the other end thereof is connected to the hot water feed pipe, or the second header pipe is connected in a manner capable of switching operation to the water feed pipe or to the hot water feed pipe through a three-way switching cock. In this case, the role of the first pipe and the first header pipe is too function as an inlet or an outlet of air in the waterreservoir, a water discharge port at overflow, or a relief port of an increased inner pressure.
Next, in the case where the apparatus is installed on the roof of a building, or the like, with the open ends of the glass container and the water-reservoir disposed higher than the sealed ends there, water is fed into the water-reservoir through the first pipe from the first header pipe connected directly to the water feed pressure source, such as water service, through the reduced pressure check valve. In this case, the water level of the stored water in the water-reservoir is raised fully independent of the length of insertion of the first pipe and, therefore, an increase in the amount of stored water is expected. In this case, the second pipe and the second header pipe act as a take-out port of hot water, and functions as an inlet or outlet of air, a relief port of an increased pressure, or a port for discharging a volume increment of hot water due to a rise in temperature and, for this reason, the hot water feed pipe, a safety valve, the automatic air discharge valve and the like are connected thereto. The inserted end of the above-mentioned first tube is disposed close to the vicinity of the sealed end of the water-reservoir. Stirring and mixing of hot water are suppressed. Furthermore, by forming an expansion chamber, or a diffuser, or calmly converting the velocity energy of fed water into the pressure energy in the vicinity of the inserted end, hot water can be taken out more efficiently.
In accordance with the vacuum type solar heat collecting apparatus of the present invention, a large quantity of water can be warmed at a time and in the case of use as a hot water storage system, the water-reservoir can be utilized as a hot water storage tank. Another hot water storage tank can be dispensed with and the initial cost of this type of apparatus can be reduced.
By making the water-reservoir with metal breakage due to thermal shock can be eliminated and required pressure-resisting strength can be maintained with light weight.
By narrowing the open and sides of the glass container and the metal water-reservoir in a small diameter, the area of seal of the open end of the glass container by the sealing fixture can be reduced and the probability of vacuum leakage of the interior can be reduced to a great extent. The expensive glass sealing fixture can be made in a smaller diameter and, by making the diameter of the metal portion having a heat conductivity larger than that of glass smaller, the heat loss from the sealing fixture can be reduced. The light receiving part is widened by a larger transparent glass portion and heat collecting efficiently is improved.
As mentioned above, the present invention enables the open ends of the glass container and the water-reservoir to be used in an upsidedown fashion. Therefore, the members can be used in common in the system wherein the open ends of the glass container and the water-reservoir are disposed lower than the sealed ends thereof and in the system wherein the open ends are disposed higher. Accordingly the present invention is advantageous for controlling production and inventory.
In one embodiment in accordance with the present invention, the header pipe of the water feed side is connected directly to the water feed pressure source through the reduced pressure check valve. The header pipe of the side of taking out hot water is connected to the hot water feed pipe having the hot water feed stopcock. Hot water can be taken out by only opening the hot water feed stopcock and, at the same time, water of an amount equal to that of the hot water taken out is fed in the water-reservoir. A special water feed controlling apparatus or the like can be dispensed with. Furthermore, needless to say, back flow of hot water can be prevented and the pressure in the hot water feeding installation can be kept at a predetermined vale. No no adverse effect is given to the pressure resisting property of the water-reservoir, pipe connecting parts and the like.